[ovs-dev] [PATCH v4 3/3] netdev-dpdk: Add TCP Segmentation Offload support

Stokes, Ian ian.stokes at intel.com
Fri Jan 17 16:30:58 UTC 2020

On 1/17/2020 4:10 PM, Ilya Maximets wrote:
> On 17.01.2020 15:23, Stokes, Ian wrote:
>> On 1/16/2020 5:00 PM, Flavio Leitner wrote:
>>> Abbreviated as TSO, TCP Segmentation Offload is a feature which enables
>>> the network stack to delegate the TCP segmentation to the NIC reducing
>>> the per packet CPU overhead.
>>> A guest using vhostuser interface with TSO enabled can send TCP packets
>>> much bigger than the MTU, which saves CPU cycles normally used to break
>>> the packets down to MTU size and to calculate checksums.
>>> It also saves CPU cycles used to parse multiple packets/headers during
>>> the packet processing inside virtual switch.
>>> If the destination of the packet is another guest in the same host, then
>>> the same big packet can be sent through a vhostuser interface skipping
>>> the segmentation completely. However, if the destination is not local,
>>> the NIC hardware is instructed to do the TCP segmentation and checksum
>>> calculation.
>>> It is recommended to check if NIC hardware supports TSO before enabling
>>> the feature, which is off by default. For additional information please
>>> check the tso.rst document.
>> Thanks for the patch Flavio,
>> Ciara has vaidated the series and no issues found on our side.
>> @Ilya, any concerns on your side? Any reason to blocking this to merge?
> I'm looking at patches now.  Will reply soon with results.
> One thing is that I'm asking to rename patches before pushing them
> to master due to incorrect 'area':
> vhost: Disable multi-segmented buffers
> -->  netdev-dpdk: Disable multi-segmented buffers for vhost.
> netdev-dpdk: Add TCP Segmentation Offload support
> -->  userspace: Add TCP Segmentation Offload support.

Thanks Ilya, your feedback is much appreciated.

> Best regards, Ilya Maximets.

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